GB2242233A

GB2242233A - Internal gear pump

Info

Publication number: GB2242233A
Application number: GB9104932A
Authority: GB
Inventors: Franz Arbogast; Peter Peiz
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1990-03-09
Filing date: 1991-03-08
Publication date: 1991-09-25
Anticipated expiration: 2011-03-08
Also published as: CH682939A5; JPH05231339A; GB2242233B; GB9104932D0; JP3135932B2; FR2665221B1; US5135371A; FR2665221A1

Abstract

The pump has an internally toothed gear 6 meshing with a driven pinion 5. The gear 6 has radial openings 17 leading from an outer peripheral surface 20 into the bases between the teeth. The width B of the pinion is greater than its pitch circle diameter do and the total cross-sectional area of the openings 17 is at least 20% of the outer surface area of the gear 6 with the total width of each opening or a plurality of openings (18, Fig. 4) to a single tooth gap being between 60 and 70% of the gear width. Sealing members (21, 23, Figs. 7 and 8) biased by the pressure of the pumped fluid may be mounted in the tooth tips. The gear 6 may be in two side-by-side parts (6a, 6a, Fig. 6). <IMAGE>

Description

k 1 INTERNAL GEAR PUMP The invention relates to a crescent-free internal

gear pump for producing high pressure. A pump of this type is known from US-2915982.

Gear pumps of known type have an internally toothed gear, with which an externally toothed pinion with a lower number of teeth is in driving engagement. Generally the toothing of such pumps is relatively narrow, relative to the diameter of the pinion or internal gear. The volumetric flow to be conveyed by the pump is determined by the height of the teeth and the width of the toothing. It is of particular importance that the cells formed by the tooth gaps in the internal gear and the teeth in the pinion is filled as completely as possible with pressure medium in the intake region of the pump.

On the outer periphery of the internal gear, the known pump comprises radial openings, through which the pressure medium may flow into the tooth gaps. The internal gear is in this case surrounded in a tight manner by a non co-rotating sleeve, which comprises a narrow slot for the distribution of the pressure medium from the intake connection of the pump to the radial openings on the internal gear. However, these radial openings have only a small axial extent in the direction of the axis of rotation of the pump, relative to the 2 axial width of the internal gear. Complete filling of the cells therefore appears possible solely if the pump is operated at a particularly low rotational speed. Otherwise the pressure medium must pass through the radial openings at a flow speed which is above values which are favourable as regards flows. If the flow speed exceeds an optimum value, which lies in a range of 1 metre/sec., then the pressure in the flowing medium adopts such low values that the air dissolved therein once more emerges and leads to the development of a considerable noise. However, in any case, a poor volumetric efficiency is involved therewith, which leads to the selection of a larger pump, if a certain delivery volume is desired.

Furthermore, in the known pump, the internal gear and the pinion are restricted laterally by sealing plates, which are pressed axially against the end faces of the pinion and internal gear. On reaching a certain pressure, despite the fact that they are pressed down axially by springs or pistons, these sealing plates may give way axially, so that the pump is not suitable for very high pressure.

It has indeed been possible with the known pump to achieve an appreciable reduction of the external dimensions in comparison with a further internal gear pump known from US-968 233. The latter is a pump whereof the cell spaces between the pinion and the internal gear 3 1 can be filled solely from both sides in the axial direction, the pressure medium being able to flow in laterally, radially outside the internal gear. Therefore, in the axial direction, the pinion and the internal gear may have only a small axial extent. Consequently, the toothed, active rotating parts of the pump take up only a small proportion of the overall length of the pump, whereas the remaining length is pressure medium occupied by the housing with the lateral inflow of the. so that even for a pump with a small delivery volume, a larger axial overall length must be tolerated. In comparison therewith, the pump according to US-915 982 is a clear improvement. However, the construction of the internal gear and of the induction port means that flow conditions are always expected, which involve excessively high flow speeds inside the pump, apart from the fact that high pressures cannot be achieved.

It is an object of the invention to improve a pump' of the aforedescribed type so that its external dimensions are further reduced and that the suction range of the pump is not a determining quantity for the overall volume of the pump, optimum values for the speed of flow being able to be maintained.

According to the invention there is provided a crescent-free internal gear pump with an internally 4 toothed gear and a pinion meshing with the internal gear and mounted to rotate in a common housing part whereof the axial extent corresponds to the width (B) of the toothing of the internal gear and of the pinion, a suction connection and a pressure connection, the internal gear being provided with radial openings which extend from an outer peripheral surface into the gaps of the toothing thereof, wherein the internal gear and the pinion are restricted in an axially sealed manner and guided laterally directly by adjacent further housing parts; the width (B) of the toothing of the pinion is at least as great as the rolling circle diameter (do) of the pinion, the entire cross-sectional area of all the openings leading through the internal gear amounts to at least 20% of the outer peripneral surface of the internal gear defined by the width (B) and the outer diameter (D) of the internal gear; the entire width (b) of the opening or openings on a single tooth gap of the internal gear amounts to between 60 and 70% of the width (B) of the toothing; and the axial width of the housing part corresponding to the width (B) of the toothing, which receives the gears actively taking part in the formation of the delivery stream, amounts to at least 40% of the entire axial length of the pump.

In contrast to known designs, on their end faces the internal gear and the pinion are restricted in an axially sealed manner and guided directly by the adjacent housing parts. Thus, the pump is suitable for producing very high pressures. Due to the fact that the entire crosssectional area of all the openings leading through the internal gear represents an at least 20% proportion of the outer peripheral surface of the internal gear and the radial openings extend over 60 to 70% of the width of the toothing, it is possible to fill the cells formed by the toothing, in the intake region, satisfactorily with pressure medium, the width of the toothing being greater than the rolling circle diameter of the pinion. Because the housing part which receives the gears actively taking part in the formation of the delivery stream takes up at least 40% of the entire axial length of the pump or of the respective housing parts the gears taking part in the delivery of the pressure medium take up a considerably higher proportion of the total structural space of the pump, so that whilst maintaining a certain maximum value for the flow speed, a pump having a higher delivery capacity is created.

By means of the radial openings on the internal gear, no hindrances to flow oppose the filling of the cells, so that the internal gear with the pinion can be considerably widened in comparison with known constructions. Thus, the width of the toothing no longer represents a determining quantity for the pump. The flow speed within the pump increases in proportion to the 6 volume delivered, thus is proportional to the product of the drive speed, external diameter and width of the internal gear. However, the flow speed is also inversely proportional to the cross-sectional area of all the radial openings cross-sectional area a certain percentage of the outer surface corresponding to the outer diameter and the width of the pinion, it can be seen that the flow speed is determined substantially solely still by the speed and by the size of the cross-sectional area of all the openings through the internal gear, thus their shape, size and number, Within the framework of a modular design and construction method, the pump flange and pump cover adjoining the central part of the pump housing on the end face, which receives the rotating parts, may remain identical with different widths of pump.

The combination of features according to the invention ensures an improved mechanical and volumetric efficiency of the pump.

It is preferable that the internal gear and the pinion should have involute toothing. The aforementioned, known pumps according to US-915 982 or 4 968 224 have circular toothing, as it is also known by the name trochoidal toothing. The advantage of such toothing is that all the teeth of the pinion mesh permanently with the sides of the trochoidal toothing of in the internal aear. By making this 7 the internal gear. Due to this individual cells having a variable volume are formed between each meshing pair of teeth, which individual cells must each be pressure-tight relative to the adjacent cell. In this case, continuous sliding takes place between the tooth tip of the pinion and the sides on the internal gear. Involute toothing, which was not customary hitherto in pumps of the aforementioned general type, can be produced more simply with conventional tools and more precisely and also has the advantage that outside the region of direct engagement, the teeth of the pinion and internal gear come out of engagement and after approximately one revolution come back into engagement along an engagement section. In this case, the engagement takes place without any rotary acceleration, which in particular favours smooth running and reduces wear. Furthermore, it is essential for involute toothing that only one side bears against the opposing side, it is thus toothing subject to play.

The radial openings may take a variety of forms. For example, the openings may extend into the region of the unloaded sides of the toothing on the internal gear and be constructed as bores lying one beside the other or as elongated slots. Along the same tooth gap in the toothing, the radial openings are preferably arranged symmetrically with respect to each other, at the same 8 spacing.

In a pump subject to play, it is known that the volumetric efficiency also depends considerably on the conditions of play in the region of the head contact between the internal gearand pinion. It is thus useful to adopt measures for improving the tightness between the tooth tips of the pinion and internal gear. This can be achieved by means of sealing members preferably on the tooth tips of the pinion. It is an advantage if on their rear side, which is remote from the tooth tip, the sealing members are connected by connecting channels to the tooth side facing the pressure region. It is thus ensured that the pressure building up in front of the tooth side is transmitted to the rear side of the sealing members and applies the latter in a sealed manner against the opposite tooth tip of the other respective gear. The sealing members may be of round or T-section and made of synthetic material preferably material which will abrade during wearing in.

In a practical construction the housing may have two end parts one of which has the bearing for the pinion shaft. These housing parts may be equipped on both sides of the internal gear with additional suction pockets for improving the suction behaviour. Due to this, a certain quantity of pressure medium may also enter from the side between the pinion and the internal gear.

From the production engineering point of view, 9 limits are set on widening of the internal gear in the d.irection of the. axis of rotation in order to increase the delivery volume of the pump, as regards precision and the surface quality of the toothing. Therefore, it may be preferred to equip the pump with two internal gears, which mesh jointly with a one-piece pinion. The Internal gears may be two substantially identical internal gears, which as regards manufacture are constructed with an optimum width and connected to each other in a non-rotary manner to act as a single internal gear in the pump.

As regards the width of its toothing, the pinion itself is generally not subject to such manufacturing restrictions as regards precision of the toothing. By means of such a widening of the pump, it is possible to increase its delivery flow, without increasing the external diameter. Nevertheless in this case it is possible to keep the flow speed within the pump at an acceptable value, for example of 1 metre/second.

A gear pump with two or more internal gears in accordance with the invention may be designed so that the axial width of the toothing amounts to at least 60% of the total axial length of the pump.

The invention will be described in detail hereafter with reference to the drawings, which show embodiments of the invention. In the drawings:

Figure 1 is a partial longitudinal section through a pump constructed in accordance with the invention; Figure 2 is a cross-section through the pump in the region of the gears thereof; Figure 3 is a detailed view in the region of the toothing of the gears of the pump; Figure 4 shows opening in the form of bores in the internal gear of the pump; Figure 5 shows openings in the form of slots in the internal gear of the pump; Figure 6 shows the construction of a double internal gear for use in the pump; Figure 7 shows the construction of sealing strips on the pinion of the pump; Figure 8 shows the construction of sealing strips on the internal gear of the pump; Figure 9 is a partial longitudinal section through a modified pump provided with additional suction pockets in the end parts of the housing.

Figures 1 and 2 show in a longitudinal section and a cross-section a crescent-free, top-sealing gear pump. The gears are subject to play, sealing respectively with one side, in the region of a central part 1 of the housing. Adjoining the part 1 on both sides are further housing parts 2 and 3. A suction connection 7 leads into the housing part 1 and a pressure connection 10 also leads into the housing part 1 from the opposite side to the suction connection 7. The entire pump with the housing parts 1, 2, 3 has an axial overall length L. An externally toothed pinion 5 attached to a drive shaft 4 meshes with an internally toothed gear 6. The toothing 12 of the pinion 5 and of the internal gear 6 has an axial width B and the pinion has a rolling circle diameter dO. The width of the toothing B is greater than the rolling circle diameter dO. The pinion 5 and the internal gear 6 are not mounted coaxially, but eccentrically with respect to each other, furthermore the pinion 5 has one tooth less than the internal gear 6, so that in each case the outer side of a tooth tip 13 on the pinion 5 comes into contact with the inside of a tooth tip 14 on the internal gear 6. Upon rotation in the direction of the arrow, the teeth on the pinion or internal gear come out of engagement. Adjoining the suction connection 7 in the central part 1 of the housing, in which the internal gear and the pinion are mounted, is a suction pocket 8 extending in the axial direction with respect to the adjacent housing parts 2 and 3. The pocket 8 extends over part of the surface 20 of the internal gear 6.

The pressure connection 10 likewise joins a pressure pocket 11 extending over a peripheral region on the internal gear 6. The inflow of pressure medium to the interior of the pump and into the tooth gap between the pinion 5 and in the internal gear 6, which brings about 12 the delivery of the pressure medium, takes place by way of radial openings 17 in the internal gear 6. These openings 17 extend from the outer surface 20 and open into the bases of the teeth of the internal gear.

Figure 3 shows a detail of the toothing 12 between the pinion 5 and internal gear 6. One of the openings 17 is shown in a cross-section through the internal gear 6.

This opening 17 penetrates the base between adjacent teeth of the internal gear 6 to lead to the tooth gap and to intersect the rear tooth flank 16 relative to the direction of rotation. The internal gear 6 is interrupted by the openings 17 in the peripheral direction over the entire width. The front tooth flank 15 driven by the pinion 5 is the loaded side, which tightness with respect to the interior and contacted by the opening 17. The openings accordingly located eccentrically with respect axes of the tooth gaps. This measure makes it to give the cross-section of the openings 17 dimensions.

Figure 4 is a view of a tooth gap in the internal gear 6. In this case, the radial openings 17 are constructed as circular bores 18 having a diameter a. Figure 5 is a similar view, where the opening 17 is constructed as an elongated slot 19. The cross-sections of passage area in each case chosen so that all the bores with the diameter a according to Figure 4 or the produces is not 17 are to the possible greater 13 elongated slot 19 according to Figure 5 with the width b amounts to between 60 and 70% of the width B of the internal gear. The total crosssectional area of all the bores 18 or the slot 19 should amount to at least 20% of the peripheral surface 20 of the internal gear.

Figure 6 shows a double internal gear 24, which consists of two internal gears 6a. The latter meshes with the pinion (not shown) of the same axial extent, but of one-piece construction. The radial openings of the peripheral surface 20 constructed as elongated openings 19 are in this case not disposed centrally within the individual internal gear 6a, but offset respectively towards the end face adjacent the other internal gear 6a. In this way, enlarged sealing surfaces 25 on the two internal gear parts 6a result on the end faces facing the end parts 2, 3 of the housing. Similar tightness between the two parts 6a of the double internal gear 24 is n ot necessary, because thin webs in this case suffice as the boundary of the openings 19.

Figures 7 and 8 are detailed views of the tooth tips 13 or 14 on the pinion 5 or the internal gear 6. Figure 7 shows on one tooth, a sealing strip 21 constructed as a circular profile, which is inserted in a groove provided along the tooth tip 13. The rear side of the sealing strip 21 is connected by way of a bore 23 to that side 15 which faces the pressure region at the time of engagement 14 with the internal gear 6. A pressure thus builds up on the rear side of the sealing strip 21, which presses the sealing strip against the opposing tooth tip of the internal gear 6. The sealing member is constructed as a T-section 22 on the adjacent tooth in Figure 7. The member 22 is also inserted in a corresponding longitudinal groove and is connected by way of a bore 23 to the tooth side 15 facing the pressure region. Figure 8 shows an appropriate arrangement of a circular sealing strip 21 or of a T-section member 22 on the tooth tips 14 of the internal gear 6. Both embodiments of the seals are alternative embodiments, which are however illustrated in the same Figures. Figure 8 also shows the openings 17 for filling the interior of the pump, the width B of the internal gear or pinion being at least as great as the rolling circle diameter dO of the pinion 5 (shown in Figures 1 and 2).

Figure 9 illustrates a pump similar to that according to Figure 1. In this case, the intake suction region 7 is enlarged in the axial direction into the housing parts 2 and 3 and constructed as suction pockets 9.

Due filling even toothing. This is an advantage if the mounting of the pinion shaft 4 in the housing parts 2 and 3 allows the construction of such suction pockets 9 without having to to this it is Possible to achieve improved in the axially outermost region of the 1 1 tolerate an enlarged total length L.

With these.features according to the invention, a pump is created which with given external dimensions has a higher delivery volume than known pumps or with given delivery volumes can be constructed with smaller external dimensions, without inadmissibly high flow speeds resulting in the pump.

1 16

Claims

1. A crescent-free internal gear pump with an internally toothed gear and a pinion meshing with the internal gear, and mounted to rotate in a common housing part whereof the axial extent corresponds to the width (B) of the toothing of the internal gear and of the pinion, a suction connection and a pressure connection, the internal gear being provided with radial openings, which extend from an outer peripheral surface into the gaps of the toothing thereof, wherein the internal gear and the pinion are restricted in an axially sealed manner and guided laterally by adjacent further housing parts; the width (B) of the toothing of the pinion is at least as great as the rolling circle diameter (do) of the pinion; the entire cross-sectional area of all the openings leading through the internal gear amounts to at least 20% of the outer peripheral surface of the internal gear defined by the width (B) and the outer diameter (D) of the internal gear; the entire width (b) of the opening or openings on a single tooth gap of the internal gear amounts to between 60 and 70% of the width (B) of the toothing; and the axial width of the housing part corresponding to the width (B) of the toothing which receives the gears actively taking part in the formation of the delivery stream, amounts to at least 40% of the entire axial length of the pump.

2. Pump according to Claim 1, wherein the internal gear 3 n i 1 17 and the pinion are provided with involute toothing.

3. Pump according to Claim 1 or 2, wherein the internal gear has one tooth more than the pinion.

4. Pump according to one of Claims 1 to 3, wherein the radial openings extend into the region of the unloaded sides of the teeth on the internal gear.

5. Pump according to one of Claims 1 to 4, wherein the radial openings are constructed as bores lying one beside the other.

6. Pump according to one of Claims 1 to 4, wherein the radial openings are constructed as elongated slots.

7. Pump according to one of Claims 5 or 6, wherein the radial openings along the same tooth gap in the toothing of the internal gear are distributed symmetrically and with the same axial spacing with respect to each other over the width (B).

8. Pump according to one of Claims 1 to 7, wherein a sealing member which may slide on the opposite tooth tip, is inserted in each of the tooth tips of one of the two gears.

9. Pump according to Claim 8, wherein the sealing members are provided on the tooth tips of the pinion.

10. Pump according to Claim 8 or 9 wherein the sealing members consist of profiled synthetic material.

11. Pump according to Claim 8, 9 or 10 wherein the sealing members are made from a synthetic material with 18 abradable properties in order to facilitate the wearing-in phase.

12. Pump according to one of Claims 8 to 11, wherein the sealing members are of round section.

13. Pump according to one of Claims 8 to 11, wherein the sealing members are sealing strips with a T-section.

14. Pump according to one of Claims 8 to 13, wherein on its rear side remote from the tooth tip, each sealing member is connected by at least one connecting channel to the tooth side facing the pressure side of the pump.

15. Pump according to one of Claims 1 to 12, wherein in the region of the suction connection, the housing comprises additional suction pockets axially beside the internal gear.

16. Pump according to one of Claims 1 to 15, wherein there are two substantially identical internal gears which jointly mesh with a single pinion.

17. Pump according to Claim 16, wherein the two internal gears are in nonrotary connection one beside the other.

18. Pump according to Claim 16 or 17, wherein the width of the housing part corresponding to the axial width (B') of the toothing of two internal gears amounts to at least 60% of the total axial length (L) of the pump.

19. A pump substantially as described with reference to, and as illustrated in any one or more of the Figures of the accompanying drawings.

Published 1991 at The Patent Office. Concept House. Cardiff Road. NeisTori. Gwent NP9 1 RH. Further copies may be obtained froni Sales Branch. Unit 6. Nine Mile Point. Cx,.mfelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques Iltd. St Mary Cray. Kent- 1